SYDNEY (AFP) - An Australian zoo on Wednesday (Oct 14) unveiled a baby chimp adopted by a pregnant female in an "unheard of" act after his mother died during birth.

The baby, whose name Boon means blessing, was orphaned when mum Soona died shortly after he was born at Monarto Zoo, south-east of Adelaide, late last week.

But in a heartwarming twist, the strong and healthy infant was immediately adopted by fellow chimp Zombi, who had remained by Soona's side as she died.

The zoo's senior primate keeper Laura Hanley said she did not know of anywhere else in the world where a pregnant chimpanzee had taken on the role of surrogate to another infant so close to a birth of her own.

"I'm humbled by what we've seen from the chimpanzee troop over the last few days - it's unheard of to see a heavily pregnant chimpanzee adopt an orphaned newborn infant," she said in a statement as the miracle baby made his public debut.

"From the minute she first cradled the newborn, she's been amazing - grooming, supporting and nursing the little man as though he was her own.

"The unique situation certainly reinforces the strong bond our chimps share and the similarities these amazing creatures have with their closest living relative, us."

Hanley said she was optimistic that Zombi would continue to care for Boon once her own baby is born later this month.